Dinosaurs (the non-bird kinds) went extinct about 66 million years ago during a global mass extinction event at the end of the Cretaceous Period.

Quick Scoop: Short Answer

  • Non-avian dinosaurs disappeared about 66 million years ago.
  • This happened at the boundary between the Cretaceous and Paleogene periods, often called the K–Pg extinction event.
  • Bird-line dinosaurs (modern birds) survived, so in a strict scientific sense, some dinosaurs are still around today as birds.

What Happened Back Then?

Most evidence points to a massive asteroid impact near what is now the Yucatán Peninsula in Mexico, forming the Chicxulub crater. This impact threw huge amounts of dust and debris into the atmosphere, blocking sunlight, cooling the planet, and collapsing food chains on land and in the oceans.

Scientists also think intense volcanic activity and longer-term climate and sea-level changes may have weakened ecosystems before the asteroid hit, making dinosaurs more vulnerable when disaster struck. In combination, these stresses triggered the end of non-avian dinosaurs and many other species.

A Bit More Nuanced

Fossils show that dinosaurs were already in some decline in parts of the world before the final extinction pulse. Still, no non-avian dinosaur fossils are found in rocks younger than about 66 million years, which is why that number is used as the cutoff for their extinction.

If you imagine Earth’s 4.5‑billion‑year history as a 24‑hour day, dinosaurs vanish in the last few minutes before midnight—while humans show up only in the final seconds.

Simple HTML Table of Key Facts

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Question Answer
How long ago did dinosaurs go extinct? About 66 million years ago.
Which dinosaurs went extinct? All non-avian (non-bird) dinosaurs.
What is the event called? Cretaceous–Paleogene (K–Pg) mass extinction.
Main cause? Large asteroid impact, plus climate and environmental changes.
Are any dinosaurs still alive? Yes, birds are considered living theropod dinosaurs.

Information gathered from public forums or data available on the internet and portrayed here.